Certain vehicles, such as the current Ford Mustang, are shipped from the factory with a drive shaft that includes at least one end that is directly bolted to an input flange forming part of either the output of the transmission or the input to the rear axle/differential. In particular, certain Ford Mustang models are delivered by the factory with a two-piece draft shaft, where the pieces of the drive shafts are interconnected by a constant velocity (CV) joint which is operative to accommodate the required relative vertical and lateral movement between the output of the transmission and the rear axle that occurs as the rear axle moves relative to the vehicle body. In the factory design, the output end of the two-piece drive shaft is directly coupled to a six bolt flange that is attached to and drives the differential pinion shaft.
It has been found that current owners and prospective owners of these types of vehicles desire to increase the power output of the engine. It has also been found that when the power output is increased, the drive shaft must be strengthened in order to accommodate the increased torque transmitted through the drive shaft: In addition, the one-piece driveshaft offers 20 lbs. less rotating mass As a result of this market demand, after market suppliers are now offering single-piece drive shafts to replace the factory supplied two-piece drive shaft. These single piece drive shafts typically include a spicer-type universal joint and flange yoke for connecting the output end of the drive shaft to the rear axle. In order to mate the drive shaft to the rear axle flange, suppliers have created adaptors that are bolted to the CV flange and which also include four threaded bores for receiving fasteners that secure a spicer-type flange yoke to the flange. It has been found that the use of an adaptor adds cost and increased probability of imbalance to this drive shaft modification. The strength of the joint between the output end of the drive shaft and the rear axle flange may also be compromised since only four bolts are used to secure the end of the drive shaft to the rear axle flange.